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Bruce,

You could calibrate the device, make the measurement of interest, go to "Stimulus", press "Pause Sweep", and the data is saved in the nanovna. The device under test can be removed and the data is preserved in the nanovna. Unfortunately, I don't seem to be able to get the serial port to work once the nanovna is connected to a computer without resetting the device which drops all of the data.

Does anyone have a cell phone application that will read data from the nanovna using an On-The-Go cable? If so, this method could bring the data into the cell phone where it could be saved.

--
Bryan, WA5VAH

there is no memory on the board to store results.

Just tested, with previous firmware version (nanoVNA_900_ch_20190802.dfu) it works ok with 5 kHz span. I tried even 10 Hz span and it works ok.

But the new firmware version (nanoVNA_900_ch_20190920.dfu) cannot works with a span smaller than 10 kHz.

The same issue happens when you trying to setup start frequency 10000 k and stop frequency 10005 k.

So, this issue was added in the latest firmware.

I am finally understanding the concept of calibrations and saving the settings/range in the nanoVNA. But I am wondering if there is any way to save results from out in the field and then recall/display them later, without having to drag a PC around with it. Or maybe that should go on a "wish list" for a firmware update.

How does one calculate the uncertainties of an out of calibration VNA and calibration kit bought on ebay?

In an ideal world everyone would do as you ask. But the nanoVNA has made it possible for people with relatively little or no VNA experience to have one. And many only have experience with hobby grade VNAs.

Even well educated people with extensive experience with professional grade VNAs often lack the mathematical skills to do completely rigorous analyses of their measurements.

I'd like to urge you to write a document describing how to do what you ask within the constraints of what is available to the individuals making the measurements. My undergraduate degree was English lit, but I'm a PhD level geophysicist with very strong mathematical skills. I don't know how to do what you ask, though I'm sure I will eventually learn. If you will create a rough draft and post it in the Files section, I'll help with polishing up your English.

Have Fun!
Reg

I've seen at least one firmware version where the minimum attainable step
size was 100Hz. I don't exactly know why, but your findings fit my
observations as well.

--
Rune

I catch some strange bug in the latest firmware. I tried to get better resolution around 26.996500 MHz to see crystal resonance. Span 10 kHz works ok. But when I trying to setup span=9 kHz or 5 kHz or any value below 10 kHz I just got strange measurement fail with saw waveform on the screen. See screenshots.

Steps to reproduce:
1) Set center frequency 26.9965 MHz
2) Set span 10 kHz and make sure all is ok
3) Set span 5 kHz and make sure there is a bug.

Any idea why it happens?

update: I tested previous firmware version nanoVNA_900_ch_20190802 and this bug is missing. So, this bug was added in the latest firmware nanoVNA_900_ch_20190920.dfu

update 2: it doesn't matter what frequency is selected for the center frequency. This bug happens when you set span smaller than 10 kHz

I tried the S21 method. Connected the 2 center pins (CH0 and CH1) to the choke ends (coax shield on both ends). -20dB at the frequency of interest is a decent common mode attenuation. -30dB is good. -40dB is excellent, but is hard to achieve.

73, Mike

Yes, that's all you need. I ran a similar case with a single strand of #22 AWG with and without the addition of the lossy core material. Although very nice particularly for looking at common mode noise suppression, you don't need the fancy test set outlined in the prior post. A measure of S11 along with S21 will demonstrate the sweet spot or corner frequency where the complex permittivity of the core material has its real part equal to its imaginary part. There will be a distinct increase in transmission and reflection loss. I did my test with perm of 4000. Corner frequency ~ 5 MHz.

Alan

Yes, I am familiar with the "other" PN systems.

Thanks for the clarification. I assumed this was test set limited, however, just to be sure.

Regards, Alan

A poor mans test jig for checking if these cheap chinese chokes do anything.
Two SMA female chassis connectors with the ground pins soldered together and a short wire connecting the center pins. The nanoVNA is calibrated with the cables connecting to the SMA connectors and the reference plane is at the end of the CH0 SMA connector.
This impedance seen from CH0 is at 100MHz without the choke 52ohm+90nH but with the choke 190ohm+190nH
It seems these chokes are doing something.

Can you show the measurement? preferably the smith chart of another VNA doing the CH0 measurement.

It makes a lot of sense.
From 0-300MHz you get the 2mA drive fundamental and its harmonics
From 300-900MHz you get8mA drive with fundamentals from 100-300MHz and its harmonics from 300-900MHz
So between 100-300MHz you see the fundamental of the 300-900MHz 3rd harmonic output.
To verify this you should do separate measurements for 0-300MHz and 300-900MHz

Bruce,
There were a couple of accompanying articles to the previous one that go into further detail.
and

It seems that CH0 output also has impedance about 40 Ohm. So, it's better to use two 10 dB attenuators. One on the CH0 and the second on CH1.

On Mon, Sep 23, 2019 at 01:15 PM, david mugridge wrote:

The 1KHz peaks are still there

The source may be DC-DC convertor. Try to disconnect external power from NanoVNA, is it still present?

I think noise may come from DC-DC converter used in battery charger. Because there is noticeable higher noise when external power supply is connected and this noise is not come through cable. It is missing when there is no external voltage.

On Mon, Sep 23, 2019 at 03:06 AM, david mugridge wrote:

The nanovna has a very strong 1KHz component - probably a result of the
1KHz codec frame-rate.

I opened the nanoVNA and connected the line in of a good USB audio device to the reference SA612. But as I did not dare to do two connections the unbalanced signal had a lot of noise. And there were 1kHz peaks independent from the selected output frequency, possibly coming from the PC itself as connecting the audio input to the ground of the nanoVNA gave the same noise.
Looking with a scope showed a very clean triangular 5kHz signal, although with some jitter that might explain some of the disturbances we see.
As disconnecting the USB resets the nanoVNA U was not able to measure with disconnected USB as I do not know how to stop the sweep (e.g.the writing to the SI5351) from the UI

Hello,

Allow us, please, to point out that to be
possible to the slightest a comparison
between measurements regarding
nanovna and/or vna, these measurements
should be accompanied by an estimation
of their uncertainty, as well as by a clearly
stated way of its calculation.

Sincerely,

yin@pez@arg

4

On Mon, Sep 23, 2019 at 07:34 AM, sala nimi wrote:

ADL5920

does only scalar measurements